Skip headers not designed to work standalone during 'make checkheaders'.

libavcodec/Makefile

@@ -651,7 +651,8 @@ OBJS-$(!CONFIG_SMALL)                  += inverse.o
 
 -include $(SUBDIR)$(ARCH)/Makefile
 
-SKIPHEADERS                             = %_tablegen.h
+SKIPHEADERS                            += %_tablegen.h aac_tablegen_decl.h \
+                                          fft-internal.h $(ARCH)/vp56_arith.h
 SKIPHEADERS-$(CONFIG_DXVA2)            += dxva2.h dxva2_internal.h
 SKIPHEADERS-$(CONFIG_LIBDIRAC)         += libdirac.h
 SKIPHEADERS-$(CONFIG_LIBSCHROEDINGER)  += libschroedinger.h